CN117199576A - Charging method of lithium battery with silicon-containing negative electrode - Google Patents

Abstract

The invention provides a charging method for a lithium battery containing a silicon negative electrode, which is characterized in that it includes a first charging stage and a second charging stage; in the first charging stage, C1 rate charging is used; in the second charging stage, using C2 rate charging; among them, C1 and C2 satisfy the following relationship: C1＝n1×n2×C2×(P1×W1)/(P1×W1+P2×W2); among them, n1＝0.3～0.7, n2＝3.6‑ 5×W1; C2=1.25~12; among them, in the silicon-containing negative electrode, the negative active material includes silicon and graphite, P1 represents the reversible capacity of silicon, P2 represents the reversible capacity of graphite, W1 represents the silicon content, and W2 represents the graphite content; in lithium During the charging process of the battery, when the SOC value of the lithium battery reaches the threshold a in the first charging stage, the first charging stage ends and switches to the second charging stage; where, a=n1×(P1×W1)/(P1×W1 +P2×W2). The charging method of the present invention is beneficial to improving the stability of silicon particles during the charging process, ensuring the long-term capacity of the silicon particles, optimizing battery cycle performance and reducing charging time.

Description

A charging method for lithium batteries containing silicon negative electrodes

Technical field

The invention belongs to the technical field of lithium batteries, and specifically relates to a charging method of a lithium battery containing a silicon negative electrode.

Background technique

Lithium precipitation is the main reason that affects the fast charging of lithium-ion batteries. Lithium precipitation means that lithium ions are directly reduced to metallic lithium on the surface of the negative electrode instead of entering the negative electrode. During the fast charging process of lithium-ion batteries, there is huge polarization inside the battery, including ohmic impedance, concentration overpotential and charge transfer overpotential, which will lead to large voltage loss.

Among the lithium-ion battery anode materials discovered so far, silicon-based materials have the highest theoretical mass specific capacity, which is 4200mAh·g ^-1 . In addition, the embedding potential of silicon-based materials into the matrix is slightly higher than that of graphite materials, and it is not easy to embed on the surface of the material. The formation of dendrites raises safety issues, which make silicon-based materials a very potential and attractive anode material.

Among the current silicon-based anode materials, silicon/graphite anode materials are widely researched and used because silicon and graphite raw materials are easy to obtain, and these two materials have relatively stable electrochemical properties. As a semiconductor material, silicon has poor ion migration ability. According to the existing ladder charging strategy, each step of fast charging usually calculates the highest rate according to the fast charging time requirements and then reduces the steps in sequence. This method starts at the beginning of fast charging. Applying a large charging rate to the battery will cause the silicon particles with poor lithium deintercalation kinetics to bear high internal stress, which will easily cause the silicon particles to break, which is not conducive to the long-term performance of the silicon-based anode material and accelerates fast charging cycles. Capacity fading during the process. And in this method, because the silicon particles cannot adapt to the rapid deintercalation rate of lithium at the beginning, the polarization phenomenon of the battery is intensified, and the input voltage cannot correspond to the charging amount, which results in ineffective loss of input energy and ultimately leads to charging the extension of time,

In view of this, it is of great practical significance to provide a charging method for lithium batteries suitable for silicon/graphite negative electrodes to improve battery cycle capacity performance and charging efficiency.

Contents of the invention

In order to solve the problems and deficiencies existing in the prior art, the present invention provides a charging method for lithium batteries containing silicon negative electrodes. This charging method is beneficial to improving the stability of silicon particles during the charging process and ensuring the long-term performance of the silicon particle capacity. Optimize battery cycle performance and reduce charging time.

The invention provides a charging method for a lithium battery containing a silicon negative electrode, which includes a first charging stage and a second charging stage; in the first charging stage, C1 rate charging is used; in the second charging stage, C2 rate charging is used; Among them, C1 and C2 satisfy the following relationship: C1=n1×n2×C2×(P1×W1)/(P1×W1+P2×W2); among them, n1=0.3～0.7, n2=3.6-5×W1; C2=1.25~12; among them, in the silicon-containing negative electrode, the negative active material includes silicon and graphite, P1 represents the silicon reversible capacity, P2 represents the graphite reversible capacity, W1 represents the silicon content, and W2 represents the graphite content; during the charging process of lithium battery , when the SOC value of the lithium battery reaches the threshold a in the first charging stage, the first charging stage ends and switches to the second charging stage; where, a=n1×(P1×W1)/(P1×W1+P2×W2 ).

In the above formula, the silicon reversible content (P1) represents the first delithiation capacity of a half-battery made of a silicon negative electrode sheet (here the silicon negative electrode sheet means that the negative active material is only silicon); the half-cell production process is as follows: take 1.5g of carbon nanotubes (CNT) and 15g of carboxymethylcellulose (CMC) glue solution with a solid content of 1.4%, then weigh 0.09g of conductive carbon black (SP), weigh 2.7g of negative active material, add 9g of water and stir evenly. Coat the obtained negative electrode slurry with a thickness of 350 μm on the negative electrode current collector and bake it at 80°C for 2 hours to obtain a negative electrode sheet; combine the above negative electrode sheet and lithium foil to form a button battery and leave it aside for at least 12 hours; the test method is as follows: let it stand for 2 hours ; 0.1C rate discharge to 5mv; 0.05C rate discharge to 5mv; 0.02C rate discharge to 5mv; 0.01C rate discharge to 5mv; 0.1C rate charge to 2V; then calculate the silicon reversible capacity. Here, silicon reversible capacity = silicon (delithiation capacity/mass of negative active material; the reversible capacity in the rate formula has been normalized to gram capacity.

Graphite reversible capacity (P2) means graphite reversible capacity refers to the first delithiation gram capacity of a half-battery made of graphite negative electrode sheet (here graphite negative electrode sheet refers to the negative active material only graphite); the half-battery production process is as follows: take 1.5g CNT and 15g solid content Homogenize 1.4% CMC glue solution, then weigh 0.09g SP, weigh 2.7g of negative active material, add 9g of water, stir, apply 350um, and bake at 80°C for 2H; combine the above negative electrode sheet and lithium foil to form a button battery. Leave it aside for at least 12 hours; the test method is as follows: leave it alone for 2 hours; discharge to 5mv at a 0.1C rate; discharge to 5mv at a 0.05C rate; discharge to 5mv at a 0.02C rate; discharge to 5mv at a 0.01C rate; charge to 2V at a 0.1C rate; then calculate Graphite reversible capacity. Here, graphite reversible capacity = graphite delithiation capacity/negative active material mass; the reversible capacity in the rate formula has been normalized to gram capacity.

The silicon content (W1) represents the proportion of the mass of silicon in the total mass of silicon and graphite; the graphite content (W2) represents the proportion of the mass of graphite in the total mass of silicon and graphite.

n1 represents the proportion of silicon pre-embedded with lithium, that is, the mass of lithium-embedded silicon accounts for the mass of all silicon; the value of n1 is a value obtained based on long-term experience; specifically, n1 lower than 0.3 will cause silicon The lithium-embedded capacity is redundant and the fast charging time is too long; n1 higher than 0.7 can easily lead to an excessively high proportion of silicon embedded with lithium per unit time, causing large internal stress inside the silicon particles. n2 represents the charging rate at the maximum current density that silicon can withstand. It is based on the value when silicon reaches 3C rate in actual testing and the corresponding silicon surface current density is unbearable. Unbearable here means that the silicon surface current density is too high. , the internal stress generated causes the silicon particles to break, exacerbating the loss of active lithium. C2 represents the maximum magnification required by the preset fast charge time, which is calculated by using the following formula: C2 = 60/preset fast charge time. The preset fast charge time is based on the fast charge time of a conventional battery being 5 to 48 minutes. calculated.

In the charging method of the lithium battery containing silicon negative electrode provided by the present invention, by first charging the lithium battery with a smaller charging rate C1, and then using a larger charging rate C2 to charge the lithium battery, it is beneficial to increase the silicon content of the lithium battery. The stability of the silicon particles in the negative electrode during the charging process improves the long-term capacity performance of the silicon particles, reduces the capacity fading rate of lithium batteries in fast charging cycles, and improves the cycle performance of lithium batteries.

The reason for the above results is that in the silicon/graphite composite negative electrode, when charging the lithium battery, the silicon will be lithiated first, that is, the lithium ions will first be embedded into the silicon particles, and if the silicon particles are charged at a larger rate, During charging, the volume expansion of silicon particles changes greatly, and due to the poor lithium ion transport kinetics of silicon, the polarization is greater. Therefore, the stability and capacity of silicon will become worse under high-rate charging, which will lead to lithium batteries. cycle performance deteriorates. In the present invention, a lower charging rate is first used to charge the battery, which allows the silicon particles to have sufficient time to embed lithium in the initial stage. In this way, the silicon particles will not bear excessive stress due to an excessive charging rate in the initial stage. The internal stress is conducive to the slow expansion of silicon particles, reducing the expansion and change volume of silicon particles, and reducing polarization. After charging the lithium battery for a certain period of time using a smaller charging rate, a certain amount of silicon particles are prelithiated to a certain extent, that is, lithium ions are embedded in a certain amount of silicon particles, and then switch to At a larger charging rate, the remaining silicon particles and graphite particles are lithiated together during charging, and graphite has better lithium ion transport dynamics than silicon, so using a larger charging rate at this time will not damage the silicon particles. Excessive internal stress is conducive to improving the stability of the silicon particles throughout the charging process, which is conducive to the capacity of the silicon particles, thus improving the overall stability of the silicon/graphite anode material and optimizing the cycle performance of the lithium battery.

Although in the prior art, a small rate is first used and then a large rate is used to charge lithium batteries, most of the charging methods in the prior art are for charging most batteries. For example, the same charging method is used to charge different batteries, but In fact, this charging method is not well adapted to every battery. Because for each different battery, the specific materials used in making the battery will be different. Furthermore, for different batteries, the active material particles have different stress capabilities, and the corresponding C1 is also different. If the same charging method is used for different batteries, it will inevitably have a certain impact on the charging performance and cycle performance of the lithium battery. Long-term use of inappropriate charging methods will cause the cycle performance of the lithium battery to deteriorate faster. . By controlling various factors that affect C1, the present invention can determine an optimal C1 value for each different lithium battery, and can provide a personalized charging method for each lithium battery, which is beneficial to the capacity of the lithium battery. long-term performance, and is beneficial to the cycle performance of lithium batteries.

In the above relational expressions about the charging rates C1 and C2 of the first charging stage and the second charging stage, the value of C2 is usually related to the fast charging required time, which is the maximum charging rate required for the fast charging required time. C2 and fast charging The time correlation of charging requirements is beneficial to setting different maximum charging rates according to customer needs. On the other hand, it is also beneficial to improve the charging efficiency of lithium batteries while ensuring the stability of silicon/graphite anode materials. In addition to being related to C2, C1 is also related to the proportion of silicon pre-embedded with lithium n1, the charging rate n2 at the maximum current density that silicon can withstand, silicon reversible capacity P1, silicon content W1, graphite reversible capacity P2 and graphite content W2. For C1, the reversible capacity of silicon has a greater impact on it, because the reversible capacity of silicon determines the kinetic properties of silicon particles deintercalating lithium ions. In the silicon/graphite composite anode, silicon particles are more ion-free than graphite particles. The migration ability is poor, and volume expansion easily causes the silicon particles to break, resulting in increased polarization. Therefore, in the silicon/graphite composite negative electrode, making C1 and C2 satisfy the above relationship will help ensure that the silicon particles have an appropriate lithium insertion speed during the initial charging process, and make the silicon particles have a higher performance at a smaller charging rate C1. Small internal pressure is not easy to break, which is beneficial to the stability of silicon particles, which is beneficial to the long-term capacity performance of silicon particles and improves the cycle performance of lithium batteries. Other factors n1, W1, P2, and W2 will also affect the lithium deintercalation performance of the entire silicon/graphite composite negative electrode to a certain extent, which will greatly affect the cycle performance of the lithium battery. Therefore, associating C1 with the above influencing factors is conducive to fully considering the lithium deintercalation performance and stability of the entire silicon/graphite composite anode, and is more conducive to obtaining a lithium battery that is more suitable for the silicon/graphite composite anode in the first charging stage. Small charging rate C1.

In addition, regarding the charging rate n2 at the maximum current density that silicon can withstand, it is related to the silicon content W1. The higher the silicon content, the smaller n2 is. This is because the higher the silicon content, the lower the first efficiency of the lithium battery, that is, the smaller the maximum current density that unit mass of silicon can withstand. Therefore, the silicon content determines the charging rate at the maximum current density that silicon can withstand. The silicon content also has an important impact on the charging performance of the entire lithium battery system.

As for when the first charging phase ends and switches to the second charging phase, it is determined based on the SOC value of the battery. When the SOC reaches the threshold b in the first charging stage, it means that a certain content of silicon in the silicon/graphite composite electrode has been embedded with lithium. The polarization of the lithium battery is relatively low, and the remaining content of silicon and graphite can be lithium-ionized at the same time. Lithium is embedded, so the graphite particles disperse part of the internal stress. Even under larger charging rates, the silicon particles will not break and have good stability. The threshold b is related to the silicon ratio n1 of pre-intercalated lithium, silicon reversible capacity P1, silicon content W1, graphite reversible capacity P2 and graphite content W2. This is considering the lithium deintercalation performance and stability performance of the silicon/graphite composite anode. These factors are highly correlated, and taking these factors into consideration will help determine the stress the silicon/graphite composite negative electrode will bear, and obtain a more appropriate threshold b, which will ensure the stability of the silicon particles while maximizing the charging of the lithium battery. efficiency.

Detailed ways

The invention provides a charging method for a lithium battery containing a silicon negative electrode, which includes a first charging stage and a second charging stage; in the first charging stage, C1 rate charging is used; in the second charging stage, C2 rate charging is used; Among them, C1 and C2 satisfy the following relationship: C1=n1×n2×C2×(P1×W1)/(P1×W1+P2×W2); among them, n1=0.3～0.7, n2=3.6-5×W1; C2=1.25~12; among them, in the silicon-containing negative electrode, the negative active material includes silicon and graphite, P1 represents the silicon reversible capacity, P2 represents the graphite reversible capacity, W1 represents the silicon content, and W2 represents the graphite content; during the charging process of lithium battery , when the SOC value of the lithium battery reaches the threshold a in the first charging stage, the first charging stage ends and switches to the second charging stage; where, a=n1×(P1×W1)/(P1×W1+P2×W2 ).

In the charging method of the lithium battery containing silicon negative electrode provided by the present invention, by first charging the lithium battery with a smaller charging rate C1, and then using a larger charging rate C2 to charge the lithium battery, it is beneficial to increase the silicon content of the lithium battery. The stability of the silicon particles in the negative electrode during the charging process improves the long-term capacity performance of the silicon particles, reduces the capacity fading rate of lithium batteries in fast charging cycles, and improves the cycle performance of lithium batteries.

The reason for the above results is that in the silicon/graphite composite negative electrode, when charging the lithium battery, the silicon will be lithiated first, that is, the lithium ions will first be embedded into the silicon particles, and if the silicon particles are charged at a larger rate, During charging, the volume expansion of silicon particles changes greatly, and due to the poor lithium ion transport kinetics of silicon, the polarization is greater. Therefore, the stability and capacity of silicon will become worse under high-rate charging, which will lead to lithium batteries. cycle performance deteriorates. In the present invention, a lower charging rate is first used to charge the battery, which allows the silicon particles to have sufficient time to embed lithium in the initial stage. In this way, the silicon particles will not bear excessive stress due to an excessive charging rate in the initial stage. The internal stress is conducive to the slow expansion of silicon particles, reducing the expansion and change volume of silicon particles, and reducing polarization. After charging the lithium battery for a certain period of time using a smaller charging rate, a certain amount of silicon particles are prelithiated to a certain extent, that is, lithium ions are embedded in a certain amount of silicon particles, and then switch to At a larger charging rate, the remaining silicon particles and graphite particles are lithiated together during charging, and graphite has better lithium ion transport dynamics than silicon, so using a larger charging rate at this time will not damage the silicon particles. Excessive internal stress is conducive to improving the stability of the silicon particles throughout the charging process, which is conducive to the capacity of the silicon particles, thus improving the overall stability of the silicon/graphite anode material and optimizing the cycle performance of the lithium battery.

Although in the prior art, a small rate is first used and then a large rate is used to charge lithium batteries, most of the charging methods in the prior art are for charging most batteries. For example, the same charging method is used to charge different batteries, but In fact, this charging method is not well adapted to every battery. Because for each different battery, the specific materials used in making the battery will be different. Furthermore, for different batteries, the active material particles have different stress capabilities, and the corresponding C1 is also different. If the same charging method is used for different batteries, it will inevitably have a certain impact on the charging performance and cycle performance of the lithium battery. Long-term use of inappropriate charging methods will cause the cycle performance of the lithium battery to deteriorate faster. . By controlling various factors that affect C1, the present invention can determine an optimal C1 value for each different lithium battery, and can provide a personalized charging method for each lithium battery, which is beneficial to the capacity of the lithium battery. long-term performance, and is beneficial to the cycle performance of lithium batteries.

In the above relational expressions about the charging rates C1 and C2 of the first charging stage and the second charging stage, the value of C2 is usually related to the fast charging required time, which is the maximum charging rate required for the fast charging required time. C2 and fast charging The time correlation of charging requirements is beneficial to setting different maximum charging rates according to customer needs. On the other hand, it is also beneficial to improve the charging efficiency of lithium batteries while ensuring the stability of silicon/graphite anode materials. In addition to being related to C2, C1 is also related to the proportion of silicon pre-embedded with lithium n1, the charging rate n2 at the maximum current density that silicon can withstand, silicon reversible capacity P1, silicon content W1, graphite reversible capacity P2 and graphite content W2. For C1, the reversible capacity of silicon has a greater impact on it, because the reversible capacity of silicon determines the kinetic properties of silicon particles deintercalating lithium ions. In the silicon/graphite composite anode, silicon particles are more ion-free than graphite particles. The migration ability is poor, and volume expansion easily causes the silicon particles to break, resulting in increased polarization. Therefore, in the silicon/graphite composite negative electrode, making C1 and C2 satisfy the above relationship will help ensure that the silicon particles have an appropriate lithium insertion speed during the initial charging process, and make the silicon particles have a higher performance at a smaller charging rate C1. Small internal pressure is not easy to break, which is beneficial to the stability of silicon particles, which is beneficial to the long-term capacity performance of silicon particles and improves the cycle performance of lithium batteries. Other factors n1, W1, P2, and W2 will also affect the lithium deintercalation performance of the entire silicon/graphite composite negative electrode to a certain extent, which will greatly affect the cycle performance of the lithium battery. Therefore, associating C1 with the above influencing factors is conducive to fully considering the lithium deintercalation performance and stability of the entire silicon/graphite composite anode, and is more conducive to obtaining a lithium battery that is more suitable for the silicon/graphite composite anode in the first charging stage. Small charging rate C1.

In addition, regarding the charging rate n2 at the maximum current density that silicon can withstand, it is related to the silicon content W1. The higher the silicon content, the smaller n2 is. This is because the higher the silicon content, the lower the first efficiency of the lithium battery, that is, the smaller the maximum current density that unit mass of silicon can withstand. Therefore, the silicon content determines the charging rate at the maximum current density that silicon can withstand. The silicon content also has an important impact on the charging performance of the entire lithium battery system.

As for when the first charging phase ends and switches to the second charging phase, it is determined based on the SOC value of the battery. When the SOC reaches the threshold b in the first charging stage, it means that a certain content of silicon in the silicon/graphite composite electrode has been embedded with lithium. The polarization of the lithium battery is relatively low, and the remaining content of silicon and graphite can be lithium-ionized at the same time. Lithium is embedded, so the graphite particles disperse part of the internal stress. Even under larger charging rates, the silicon particles will not break and have good stability. The threshold b is related to the silicon ratio n1 of pre-intercalated lithium, silicon reversible capacity P1, silicon content W1, graphite reversible capacity P2 and graphite content W2. This is considering the lithium deintercalation performance and stability performance of the silicon/graphite composite anode. These factors are highly correlated, and taking these factors into consideration will help determine the stress the silicon/graphite composite negative electrode will bear, and obtain a more appropriate threshold b, which will ensure the stability of the silicon particles while maximizing the charging of the lithium battery. efficiency.

Preferably, W1=0.01～0.5, W2=1-W1, n2=1.1～3.55.

Preferably, P1=1500～2000mAh/g, P2=330～370mAh/g.

Preferably, n1=0.4～0.6.

Preferably, n2=2.5～3.55.

When n1 or n2 are respectively within the above numerical range, it is more conducive to adjust the value of C1 to be more suitable for the first charging stage, which can not only ensure that the silicon particles are not broken by excessive internal stress when being prelithiated, but also ensure that Silicon can be prelithiated faster, shortening the first-stage charging time and thus improving the charging efficiency of the entire charging process.

Preferably, in the first charging stage, the SOC of the initial charge of the lithium battery is <20%. Ensure that in the first charging stage, the SOC of the initial charging of the lithium battery meets the above conditions, ensuring that all lithium ions can be embedded in the silicon particles during the first charging stage, and ensuring that a sufficient proportion of the silicon particles are prelithiated. , ensuring that when entering the second charging stage, lithium ions can be embedded in lithium by the remaining silicon particles and graphite particles at the same time, so that the graphite particles can effectively share part of the internal stress under large charging rates, avoid the easy breakage of the silicon particles, and improve the stability of the silicon particles. sex.

Preferably, before the first charging stage, a pre-charging stage is also included; when the pre-charging stage ends, the SOC of the lithium battery is <10%.

Preferably, in the first charging stage, the peak value of the current density on the surface of the silicon-containing negative electrode is no more than 9.2 mA·cm ^-2 . The current density on the surface of the silicon-containing negative electrode here represents the current that the negative electrode can withstand per unit area density. Ensuring that the current density on the surface of the silicon-containing negative electrode meets the above conditions can ensure that the particles in the silicon-containing negative electrode are not easily broken, which is beneficial to ensuring the stability of the silicon-containing negative electrode during the charging process and improving the cycle stability of lithium batteries.

Preferably, in the second charging stage, the peak value of the current density on the surface of the silicon-containing negative electrode is not less than bmA·cm ^-2 , b=4.6×C1. Making the peak current density on the surface of the silicon-containing anode meet the above conditions in the second charging stage not only ensures that the lithium battery can be charged quickly and improves the charging efficiency, but also facilitates the stability of the silicon-containing anode during the entire charging process. Capacity development and cycle performance of lithium batteries.

Preferably, C1=0.2～2C. Keeping C1 within the above numerical range is beneficial to ensuring the stability of the silicon particles in the silicon-based negative electrode during the first charging process, and is beneficial to the long-term capacity performance of silicon.

Preferably, in the silicon-containing negative electrode, W1=0.1~0.3. Ensure that the silicon content in the silicon-containing negative electrode is within the above range. On the one hand, it can avoid that too little silicon content cannot effectively increase the capacity of lithium batteries. On the other hand, it can also avoid that too much silicon content can cause silicon/graphite composite negative electrodes. The overall expansion rate increases, deteriorating the cycle performance of lithium batteries.

Preferably, in the second charging stage, the charging rate is sequentially reduced according to the highest rate C2.

Preferably, at the end of the second charging stage, the SOC of the lithium battery is not less than 80%.

Preferably, the above charging method for a lithium battery containing a silicon negative electrode further includes a third charging stage; in the third charging stage, the initial SOC of the lithium battery is not less than 80%.

Preferably, the lithium battery further includes a positive electrode, the positive electrode includes a positive electrode active material, and the positive electrode active material includes a nickel-cobalt-manganese ternary material.

According to another aspect of the present invention, a lithium battery charging device is provided, which adopts the above-mentioned charging method of a lithium battery containing a silicon negative electrode.

In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only embodiments of a part of the present invention, rather than All examples.

The following examples and comparative examples are mainly based on selecting different lithium batteries for charging, and by controlling the parameters that affect charging in each example and comparative example, the charging method provided by the present invention is explored on the charging time and cycle performance of lithium batteries. Impact.

Example 1

1. Relevant parameters of lithium battery

Through relevant tests and calculations, the relevant parameters of the lithium battery in this embodiment are as follows: the reversible silicon content P1 is 1600mAh·g ^-1 , the reversible graphite content P2 is 350mAh·g ^-1 , the silicon content W1 is 0.1, and the graphite content W2 is 0.9, the threshold a is 0.236, the proportion of silicon pre-embedded with lithium n1 is 0.7, the charging rate n2 at the maximum current density that silicon can withstand is 2.7, C1 in the first charging stage is 1.9C, and C2 in the second charging stage is set for 3C.

2.Charging of lithium battery

Follow the steps below to charge the lithium battery:

(1) Pre-charging stage: charge the lithium battery to 5% SOC at 0.33C;

(2) First charging stage: then charge the lithium battery to 23.6% SOC at 1.9C;

(3) Second charging stage: Then use 3C as the highest charging rate, and charge the lithium battery to 80% SOC in a step-down manner of reducing 0.2C each time. The final cut-off charging rate of the second charging stage is 1.4C;

(4) The third charging stage: Finally, charge the lithium battery to 100% SOC at 0.33C.

Among them, in the second charging stage, the specific charging operations of the lithium battery are as follows: ① charge from 23.6% SOC to 40% SOC at 3C; ② charge from 40% SOC to 42% SOC at 2.8C; ③ charge from 42% SOC to 42% SOC at 2.6C % SOC to 45% SOC; ④ Charge from 45% SOC to 50% SOC at 2.4C; ⑤ Charge from 50% SOC to 60% SOC at 2.2C; ⑥ Charge from 60% SOC to 65% SOC at 2.0C; ⑦ Charge from 65% SOC to 68% SOC at 1.8C; ⑧ Charge from 68% SOC to 70% SOC at 1.6C; ⑨ Charge from 70% SOC to 80% SOC at 1.4C.

In addition, the charging time is taken as the first charging time, and the charging time is recorded.

3. Lithium battery cycle test process

Follow the steps below to perform cycle performance testing on lithium batteries:

Step 1: Let the lithium battery stand for 2 hours at 25°C to allow it to reach thermal equilibrium;

Step 2: Discharge the lithium battery to 2.8V at 1/3C;

Step 3: Leave the lithium battery for 30 minutes;

Step 4: Charge the lithium battery using the above charging method (refer to 2. Charging of lithium batteries);

Step 5: Let the lithium battery stand for 10 minutes;

Step 6: Repeat steps 2 to 5 until the battery health status reaches 80% SOH.

Example 2

1. Relevant parameters of lithium battery

Through relevant tests and calculations, the relevant parameters of the lithium battery in this embodiment are as follows: the reversible silicon content P1 is 1600mAh·g ^-1 , the reversible graphite content P2 is 350mAh·g ^-1 , the silicon content W1 is 0.1, and the graphite content W2 is 0.9, the threshold a is 0.202, the proportion of silicon pre-embedded with lithium n1 is 0.6, the charging rate n2 at the maximum current density that silicon can withstand is 2.7, C1 in the first charging stage is 1.6C, and C2 in the second charging stage is set for 3C.

2.Charging of lithium battery

Follow the steps below to charge the lithium battery:

(1) Pre-charging stage: charge the lithium battery to 5% SOC at 0.33C;

(2) First charging stage: then charge the lithium battery to 20.2% SOC at 1.6C;

(3) Second charging stage: Then use 3C as the highest charging rate, and charge the lithium battery to 80% SOC in a step-down manner of reducing 0.2C each time. The final cut-off charging rate of the second charging stage is 1.4C;

(4) The third charging stage: Finally, charge the lithium battery to 100% SOC at 0.33C.

Among them, in the second charging stage, in the specific charging operation of the lithium battery, 3C is used to charge from 20.2% SOC to 40% SOC in ①, and the remaining step reduction conditions are consistent with Embodiment 1.

In addition, the charging time is taken as the first charging time, and the charging time is recorded.

3. Lithium battery cycle test process

The cycle performance test of the lithium battery in this example is consistent with Example 1.

Example 3

1. Relevant parameters of lithium battery

Through relevant tests and calculations, the relevant parameters of the lithium battery in this embodiment are as follows: the reversible silicon content P1 is 600mAh·g ^-1 , the reversible graphite content P2 is 350mAh·g ^-1 , the silicon content W1 is 0.1, and the graphite content W2 is 0.9, the threshold a is 0.135, the proportion of silicon pre-embedded with lithium n1 is 0.4, the charging rate n2 at the maximum current density that silicon can withstand is 2.7, C1 in the first charging stage is 1.1C, and C2 in the second charging stage is set for 3C.

2.Charging of lithium battery

Follow the steps below to charge the lithium battery:

(1) Pre-charging stage: charge the lithium battery to 5% SOC at 0.33C;

(2) First charging stage: Then charge the lithium battery to 13.5% SOC at 1.1C;

(3) Second charging stage: Then use 3C as the highest charging rate, and charge the lithium battery to 80% SOC in a step-down manner of reducing 0.2C each time. The final cut-off charging rate of the second charging stage is 1.4C;

(4) The third charging stage: Finally, charge the lithium battery to 100% SOC at 0.33C.

Among them, in the second charging stage, in the specific charging operation of the lithium battery, 3C is used to charge from 13.5% SOC to 40% SOC in ①, and the remaining step reduction conditions are consistent with Embodiment 1.

In addition, the charging time is taken as the first charging time, and the charging time is recorded.

3. Lithium battery cycle test process

The cycle performance test of the lithium battery in this example is consistent with Example 1.

Example 4

1. Relevant parameters of lithium battery

Through relevant tests and calculations, the relevant parameters of the lithium battery in this embodiment are as follows: the reversible silicon content P1 is 1600mAh·g ^-1 , the reversible graphite content P2 is 350mAh·g ^-1 , the silicon content W1 is 0.1, and the graphite content W2 is 0.9, the threshold a is 0.101, the proportion of silicon pre-embedded with lithium n1 is 0.3, the charging rate n2 at the maximum current density that silicon can withstand is 2.7, C1 in the first charging stage is 0.8C, and C2 in the second charging stage is set for 3C.

2.Charging of lithium battery

Follow the steps below to charge the lithium battery:

(1) Pre-charging stage: charge the lithium battery to 5% SOC at 0.33C;

(2) First charging stage: then charge the lithium battery to 10.1% SOC at 0.8C;

(3) Second charging stage: Then use 3C as the highest charging rate, and charge the lithium battery to 80% SOC in a step-down manner of reducing 0.2C each time. The final cut-off charging rate of the second charging stage is 1.4C;

(4) The third charging stage: Finally, charge the lithium battery to 100% SOC at 0.33C.

Among them, in the second charging stage, in the specific charging operation of the lithium battery, 3C is used to charge from 10.1% SOC to 40% SOC in ①, and the remaining step reduction conditions are consistent with Embodiment 1.

In addition, the charging time is taken as the first charging time, and the charging time is recorded.

3. Lithium battery cycle test process

The cycle performance test of the lithium battery in this example is consistent with Example 1.

Example 5

1. Relevant parameters of lithium battery

Through relevant tests and calculations, the relevant parameters of the lithium battery in this embodiment are as follows: the reversible silicon content P1 is 600mAh·g ^-1 , the reversible graphite content P2 is 350mAh·g ^-1 , the silicon content W1 is 0.1, and the graphite content W2 is 0.9, the threshold a is 0.168, the proportion of silicon pre-embedded with lithium n1 is 0.5, the charging rate n2 at the maximum current density that silicon can withstand is 3.55, C1 in the first charging stage is 1.8C, and C2 in the second charging stage is set for 3C.

2.Charging of lithium battery

Follow the steps below to charge the lithium battery:

(1) Pre-charging stage: charge the lithium battery to 5% SOC at 0.33C;

(2) First charging stage: then charge the lithium battery to 16.8% SOC at 1.8C;

(3) Second charging stage: Then use 3C as the highest charging rate, and charge the lithium battery to 80% SOC in a step-down manner of reducing 0.2C each time. The final cut-off charging rate of the second charging stage is 1.4C;

(4) The third charging stage: Finally, charge the lithium battery to 100% SOC at 0.33C.

Among them, in the second charging stage, in the specific charging operation of the lithium battery, 3C is used to charge from 16.8% SOC to 40% SOC in ①, and the remaining step reduction conditions are consistent with Embodiment 1.

In addition, the charging time is taken as the first charging time, and the charging time is recorded.

3. Lithium battery cycle test process

The cycle performance test of the lithium battery in this example is consistent with Example 1.

Example 6

1. Relevant parameters of lithium battery

Through relevant tests and calculations, the relevant parameters of the lithium battery in this embodiment are as follows: the reversible silicon content P1 is 1600mAh·g ^-1 , the reversible graphite content P2 is 350mAh·g ^-1 , the silicon content W1 is 0.1, and the graphite content W2 is 0.9, the threshold a is 0.168, the proportion of silicon pre-embedded with lithium n1 is 0.5, the charging rate n2 at the maximum current density that silicon can withstand is 3.5, the C1 of the first charging stage is 1.78C, and the C2 setting of the second charging stage for 3C.

2.Charging of lithium battery

Follow the steps below to charge the lithium battery:

(1) Pre-charging stage: charge the lithium battery to 5% SOC at 0.33C;

(2) First charging stage: Then charge the lithium battery to 16.8% SOC at 1.78C;

(3) Second charging stage: Then use 3C as the highest charging rate, and charge the lithium battery to 80% SOC in a step-down manner of reducing 0.2C each time. The final cut-off charging rate of the second charging stage is 1.4C;

(4) The third charging stage: Finally, charge the lithium battery to 100% SOC at 0.33C.

Among them, in the second charging stage, in the specific charging operation of the lithium battery, 3C is used to charge from 16.8% SOC to 40% SOC in ①, and the remaining step reduction conditions are consistent with Embodiment 1.

In addition, the charging time is taken as the first charging time, and the charging time is recorded.

3. Lithium battery cycle test process

The cycle performance test of the lithium battery in this example is consistent with Example 1.

Example 7

1. Relevant parameters of lithium battery

Through relevant tests and calculations, the relevant parameters of the lithium battery in this embodiment are as follows: the reversible silicon content P1 is 1600mAh·g ^-1 , the reversible graphite content P2 is 350mAh·g ^-1 , the silicon content W1 is 0.1, and the graphite content W2 is 0.9, the threshold a is 0.168, the proportion of silicon pre-embedded with lithium n1 is 0.5, the charging rate n2 at the maximum current density that silicon can withstand is 2.5, C1 in the first charging stage is 1.3C, and C2 in the second charging stage is set for 3C.

2.Charging of lithium battery

Follow the steps below to charge the lithium battery:

(1) Pre-charging stage: charge the lithium battery to 5% SOC at 0.33C;

(2) First charging stage: then charge the lithium battery to 16.8% SOC at 1.3C;

(3) Second charging stage: Then use 3C as the highest charging rate, and charge the lithium battery to 80% SOC in a step-down manner of reducing 0.2C each time. The final cut-off charging rate of the second charging stage is 1.4C;

(4) The third charging stage: Finally, charge the lithium battery to 100% SOC at 0.33C.

Among them, in the second charging stage, in the specific charging operation of the lithium battery, 3C is used to charge from 16.8% SOC to 40% SOC in ①, and the remaining step reduction conditions are consistent with Embodiment 1.

In addition, the charging time is taken as the first charging time, and the charging time is recorded.

3. Lithium battery cycle test process

The cycle performance test of the lithium battery in this example is consistent with Example 1.

Example 8

1. Relevant parameters of lithium battery

Through relevant tests and calculations, the relevant parameters of the lithium battery in this embodiment are as follows: the reversible silicon content P1 is 1600mAh·g ^-1 , the reversible graphite content P2 is 350mAh·g ^-1 , the silicon content W1 is 0.1, and the graphite content W2 is 0.9, the threshold a is 0.168, the proportion of silicon pre-embedded with lithium n1 is 0.5, the charging rate n2 at the maximum current density that silicon can withstand is 1.1, C1 in the first charging stage is 0.6C, and C2 in the second charging stage is set for 3C.

2.Charging of lithium battery

Follow the steps below to charge the lithium battery:

(1) Pre-charging stage: charge the lithium battery to 5% SOC at 0.33C;

(2) First charging stage: then charge the lithium battery to 16.8% SOC at 0.6C;

(3) Second charging stage: Then use 3C as the highest charging rate, and charge the lithium battery to 80% SOC in a step-down manner of reducing 0.2C each time. The final cut-off charging rate of the second charging stage is 1.4C;

(4) The third charging stage: Finally, charge the lithium battery to 100% SOC at 0.33C.

Among them, in the second charging stage, the downgrading situation in the specific charging operation of the lithium battery is consistent with Embodiment 1.

In addition, the charging time is taken as the first charging time, and the charging time is recorded.

3. Lithium battery cycle test process

The cycle performance test of the lithium battery in this example is consistent with Example 1.

Example 9

1. Relevant parameters of lithium battery

Through relevant tests and calculations, the relevant parameters of the lithium battery in this embodiment are as follows: the reversible silicon content P1 is 1600mAh·g ^-1 , the reversible graphite content P2 is 350mAh·g ^-1 , the silicon content W1 is 0.15, and the graphite content W2 is 0.85, the threshold a is 0.237, the proportion of silicon pre-embedded with lithium n1 is 0.7, the charging rate n2 at the maximum current density that silicon can withstand is 2.7, C1 in the first charging stage is 1.9C, and C2 in the second charging stage is set for 3C.

2.Charging of lithium battery

Follow the steps below to charge the lithium battery:

(1) Pre-charging stage: charge the lithium battery to 5% SOC at 0.33C;

(2) First charging stage: then charge the lithium battery to 23.7% SOC at 1.9C;

(3) Second charging stage: Then use 3C as the highest charging rate, and charge the lithium battery to 80% SOC in a step-down manner of reducing 0.2C each time. The final cut-off charging rate of the second charging stage is 0.4C;

(4) The third charging stage: Finally, charge the lithium battery to 100% SOC at 0.33C.

Among them, in the second charging stage, in the specific charging operation of the lithium battery, 3C is used to charge from 23.7% SOC to 40% SOC in ①, and the remaining step reduction conditions are consistent with Embodiment 1.

In addition, the charging time is taken as the first charging time, and the charging time is recorded.

3. Lithium battery cycle test process

The cycle performance test of the lithium battery in this example is consistent with Example 1.

Example 10

1. Relevant parameters of lithium battery

Through relevant tests and calculations, the relevant parameters of the lithium battery in this embodiment are as follows: the reversible silicon content P1 is 1600mAh·g ^-1 , the reversible graphite content P2 is 350mAh·g ^-1 , the silicon content W1 is 0.1, and the graphite content W2 is 0.9, the threshold a is 0.168, the proportion of silicon pre-embedded with lithium n1 is 0.5, the charging rate n2 at the maximum current density that silicon can withstand is 3.7, C1 in the first charging stage is 0.4C, and C2 in the second charging stage is set for 3C.

2.Charging of lithium battery

Follow the steps below to charge the lithium battery:

(1) Pre-charging stage: charge the lithium battery to 5% SOC at 0.33C;

(2) First charging stage: then charge the lithium battery to 16.8% SOC at 1.9C;

(3) Second charging stage: Then use 3C as the highest charging rate, and charge the lithium battery to 80% SOC in a step-down manner of reducing 0.2C each time. The final cut-off charging rate of the second charging stage is 0.4C;

(4) The third charging stage: Finally, charge the lithium battery to 100% SOC at 0.33C.

Among them, in the second charging stage, in the specific charging operation of the lithium battery, 3C is used to charge from 16.8% SOC to 40% SOC in ①, and the remaining step reduction conditions are consistent with Embodiment 1.

In addition, the charging time is taken as the first charging time, and the charging time is recorded.

3. Lithium battery cycle test process

The cycle performance test of the lithium battery in this example is consistent with Example 1.

Example 11

1. Relevant parameters of lithium battery

Through relevant tests and calculations, the relevant parameters of the lithium battery in this embodiment are as follows: the reversible silicon content P1 is 1600mAh·g ^-1 , the reversible graphite content P2 is 350mAh·g ^-1 , the silicon content W1 is 0.1, and the graphite content W2 is 0.9, the threshold a is 0.168, the proportion of silicon pre-embedded with lithium n1 is 0.5, the charging rate n2 at the maximum current density that silicon can withstand is 0.8, C1 in the first charging stage is 1.9C, and C2 in the second charging stage is set for 3C.

2.Charging of lithium battery

Follow the steps below to charge the lithium battery:

(1) Pre-charging stage: charge the lithium battery to 5% SOC at 0.33C;

(2) First charging stage: then charge the lithium battery to 16.8% SOC at 0.4C;

(3) Second charging stage: Then use 3C as the highest charging rate, and charge the lithium battery to 80% SOC in a step-down manner of reducing 0.2C each time. The final cut-off charging rate of the second charging stage is 1.4C;

(4) The third charging stage: Finally, charge the lithium battery to 100% SOC at 0.33C.

Among them, in the second charging stage, in the specific charging operation of the lithium battery, 3C is used to charge from 16.8% SOC to 40% SOC in ①, and the remaining step reduction conditions are consistent with Embodiment 1.

In addition, the charging time is taken as the first charging time, and the charging time is recorded.

3. Lithium battery cycle test process

The cycle performance test of the lithium battery in this example is consistent with Example 1.

Example 12

1. Relevant parameters of lithium battery

The relevant parameters of the lithium battery in this embodiment are consistent with those in Embodiment 1 except for C2, where C2 is set to 2C.

2.Charging of lithium battery

Follow the steps below to charge the lithium battery:

(1) Pre-charging stage: charge the lithium battery to 5% SOC at 0.33C;

(2) First charging stage: then charge the lithium battery to 23.6% SOC at 1.9C;

(3) Second charging stage: Then use 2C as the highest charging rate, and charge the lithium battery to 80% SOC in a step-down manner of reducing 0.2C each time. The final cut-off charging rate of the second charging stage is 0.4C;

(4) The third charging stage: Finally, charge the lithium battery to 100% SOC at 0.33C.

Among them, in the second charging stage, the specific charging operations of the lithium battery are as follows: ① Charge from 23.6% SOC to 65% SOC at 2C; ② Charge from 65% SOC to 68% SOC at 1.8C; ③ From 68% to 68% SOC at 1.6C % SOC charging to 70% SOC; ④ charging from 70% SOC to 80% SOC at 1.4C; ⑤ charging from 80% SOC to 100% SOC at 0.33C.

In addition, the charging time is taken as the first charging time, and the charging time is recorded.

3. Lithium battery cycle test process

The cycle performance test of the lithium battery in this example is consistent with Example 1.

Comparative example 1

1. Relevant parameters of lithium battery

This comparison example directly uses high-rate C2 to charge the lithium battery, so there is no first charging stage with small-rate C1. That is, the lithium battery directly enters the second charging stage after going through the pre-charging stage, and C2 in the second charging stage is set to 3C. The relevant parameters of the lithium battery in this comparative example are as follows: the reversible silicon content P1 is 1600mAh·g ^-1 , the reversible graphite content P2 is 350mAh·g ^-1 , the silicon content W1 is 0.1, and the graphite content W2 is 0.9.

2.Charging of lithium battery

Follow the steps below to charge the lithium battery:

(1) Pre-charging stage: charge the lithium battery to 5% SOC at 0.33C;

(2) Second charging stage: Then use 3C as the highest charging rate, and charge the lithium battery to 80% SOC in a step-down manner of reducing 0.2C each time. The final cut-off charging rate of the second charging stage is 0.4C;

(3) The third charging stage: Finally, charge the lithium battery to 100% SOC at 0.33C.

Among them, in the second charging stage, the specific charging operations of the lithium battery are as follows: ① charge from 5% SOC to 40% SOC at 3C; ② charge from 40% SOC to 42% SOC at 2.8C; ③ charge from 42% SOC to 42% SOC at 2.6C. % SOC to 45% SOC; ④ Charge from 45% SOC to 50% SOC at 2.4C; ⑤ Charge from 50% SOC to 60% SOC at 2.2C; ⑥ Charge from 60% SOC to 65% SOC at 2.0C; ⑦ Charge from 65% SOC to 68% SOC at 1.8C; ⑧ Charge from 68% SOC to 70% SOC at 1.6C; ⑨ Charge from 70% SOC to 80% SOC at 1.4C.

In addition, the charging time is taken as the first charging time, and the charging time is recorded.

3. Lithium battery cycle test process

The cycle performance test of the lithium battery in this comparative example is consistent with Example 1.

Comparative example 2

1. Relevant parameters of lithium battery

Through relevant tests and calculations, the relevant parameters of the lithium battery in this comparative example are as follows: silicon reversible content P1 is 1600mAh·g ^-1 , graphite reversible content P2 is 350mAh·g ^-1 , silicon content W1 is 0.1, graphite content W2 is 0.9, the threshold a is 0.303, the proportion of silicon pre-embedded with lithium n1 is 0.9, the charging rate n2 at the maximum current density that silicon can withstand is 3, C1 in the first charging stage is 2.7C, and C2 in the second charging stage Set to 3C.

2.Charging of lithium battery

Follow the steps below to charge the lithium battery:

(1) Pre-charging stage: charge the lithium battery to 5% SOC at 0.33C;

(2) First charging stage: then charge the lithium battery to 30.3% SOC at 2.7C;

(3) Second charging stage: Then use 3C as the highest charging rate, and charge the lithium battery to 80% SOC in a reduced-step manner by reducing 0.2C each time. The final cut-off charging rate of the second charging stage is 0.4C; ( 4) The third charging stage: Finally, charge the lithium battery to 100% SOC at 0.33C.

Among them, in the second charging stage, in the specific charging operation of the lithium battery, 3C is used to charge from 30.3% SOC to 40% SOC in ①, and the remaining step reduction conditions are consistent with Embodiment 1.

In addition, the charging time is taken as the first charging time, and the charging time is recorded.

3. Lithium battery cycle test process

The cycle performance test of the lithium battery in this comparative example is consistent with Example 1.

Comparative example 3

1. Relevant parameters of lithium battery

Through relevant tests and calculations, the relevant parameters of the lithium battery in this comparative example are as follows: silicon reversible content P1 is 1600 mAh·g ^-1 , graphite reversible content P2 is 350mAh·g ^-1 , silicon content W1 is 0.1, graphite content W2 is 0.9, the threshold a is 0.067, the proportion of silicon pre-embedded with lithium n1 is 0.2, the charging rate n2 at the maximum current density that silicon can withstand is 3, C1 in the first charging stage is 0.6C, and C1 in the second charging stage C2 is set to 3C.

2.Charging of lithium battery

Follow the steps below to charge the lithium battery:

(1) Pre-charging stage: charge the lithium battery to 5% SOC at 0.33C;

(2) First charging stage: then charge the lithium battery to 6.7% SOC at 0.6C;

(3) Second charging stage: Then use 3C as the highest charging rate, and charge the lithium battery to 80% SOC in a reduced-step manner by reducing 0.2C each time. The final cut-off charging rate of the second charging stage is 0.4C; ( 4) The third charging stage: Finally, charge the lithium battery to 100% SOC at 0.33C.

Among them, in the second charging stage, in the specific charging operation of the lithium battery, 3C is used to charge from 6.7% SOC to 40% SOC in ①, and the remaining step reduction conditions are consistent with Embodiment 1.

In addition, the charging time is taken as the first charging time, and the charging time is recorded.

3. Lithium battery cycle test process

The cycle performance test of the lithium battery in this comparative example is consistent with Example 1.

Test Results

Table 1 below is about the relevant parameters and cycle performance test results of the batteries in the above embodiments and comparative examples.

Table 1 Relevant parameters and cycle performance test results of batteries in Examples and Comparative Examples

It can be seen from Table 1 that charging lithium batteries using the charging method of the present invention can not only achieve rapid charging of lithium batteries, but also achieve better cycle performance of lithium batteries. Please refer to the data in Table 1. This is because in the charging method of the present invention, by first charging the lithium battery with a smaller charging rate C1, and then using a larger charging rate C2 to charge the lithium battery, it is beneficial to increase the silicon particles in the silicon-containing negative electrode. The stability during the charging process makes the silicon particles less likely to break, improves the long-term capacity performance of the silicon particles, and reduces the capacity fading rate of lithium batteries in fast charging cycles, which is beneficial to reducing charging time while improving the cycle performance of lithium batteries. . Moreover, the charging method in the present invention can determine an optimal C1 value for each different lithium battery by controlling various factors that affect C1, and can provide a personalized charging method for each lithium battery. It is beneficial to the long-term performance of lithium battery capacity and the cycle performance of lithium batteries.

It can be seen from Examples 1 to 6 that the value of n1 has an impact on the balance between charging time and cycle performance of lithium batteries. When n1 is between 0.4 and 0.6, it is more beneficial to the charging time and cycle performance of lithium batteries. The balance of performance can further optimize the cycle performance of the battery while achieving shorter charging time.

It can be seen from Examples 5, 6, 7, and 8 that the value of n2 also has a certain impact on the balance between charging time and cycle performance of lithium batteries. When n2 is between 2.5 and 3.55, it is more beneficial. Balancing charging time and cycle performance of lithium batteries. In Comparative Example 1, high-rate C2 is directly used to charge the lithium battery. The silicon particles are suddenly subjected to excessive stress, causing the silicon particles to be easily broken and the stability to be reduced, thus degrading the cycle performance of the lithium battery. In Comparative Examples 2 and 3, the value of n1 is not between 0.3 and 0.7, so the cycle performance or charging time of the lithium battery has deteriorated to a certain extent. This shows that keeping n1 within the appropriate range will improve the charging time and cycle performance of the lithium battery. The balance is of great significance.

The above embodiments are only used to illustrate the technical solutions of the present invention and do not limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be carried out. modifications or equivalent substitutions, but these modifications or substitutions are within the protection scope of the present invention.

Claims (12)

1. A charging method for a lithium battery containing a silicon negative electrode, characterized in that it includes a first charging stage and a second charging stage; In the first charging stage, C1 rate charging is used; in the second charging stage, C2 rate charging is used; Among them, C1 and C2 satisfy the following relationship: C1=n1×n2×C2×(P1×W1)/(P1×W1+P2×W2); Among them, n1=0.3~0.7, n2=3.6-5×W1; C2=1.25~12; Among them, in the silicon-containing negative electrode, the negative active material includes silicon and graphite, P1 represents the silicon reversible capacity, P2 represents the graphite reversible capacity, W1 represents the silicon content, and W2 represents the graphite content; During the charging process of the lithium battery, when the SOC value of the lithium battery reaches the threshold value a in the first charging stage, the first charging stage ends and switches to the second charging stage; Among them, a=n1×(P1×W1)/(P1×W1+P2×W2). 2. The charging method of lithium battery containing silicon negative electrode according to claim 1, characterized in that: W1=0.01~0.5, W2=1-W1, n2=1.1~3.55. 3. The charging method of lithium battery containing silicon negative electrode according to claim 1, characterized in that: P1=1500~2000mAh/g, P2=330~370mAh/g. 4. The charging method of lithium battery containing silicon negative electrode according to claim 1, characterized in that: n1=0.4～0.6. 5. The charging method of lithium battery containing silicon negative electrode according to claim 2, characterized in that: n2=2.5~3.55. 6. The charging method of a lithium battery containing a silicon negative electrode according to claim 1, wherein in the first charging stage, the SOC of the initial charging of the lithium battery is <20%. 7. The charging method of lithium battery containing silicon negative electrode according to claim 6, characterized in that: before the first charging stage, it also includes a pre-charging stage; When the pre-charging phase ends, the SOC of the lithium battery is <10%. 8. The charging method of a lithium battery containing a silicon-containing negative electrode according to claim 1, characterized in that: in the first charging stage, the peak value of the current density on the surface of the silicon-containing negative electrode is not greater than 9.2 mA·cm ^-2 . 9. The charging method of a lithium battery containing a silicon-containing negative electrode according to claim 8, characterized in that: in the second charging stage, the peak value of the current density on the surface of the silicon-containing negative electrode is not less than b mA·cm ^-2 , b=4.6×C1. 10. The charging method of lithium battery containing silicon negative electrode according to claim 1, characterized in that: C1=0.6~2C. 11. The charging method of a lithium battery containing a silicon-containing negative electrode according to claim 2, characterized in that: in the silicon-containing negative electrode, W1=0.1˜0.3. 12. A lithium battery charging device, characterized in that the charging method of a lithium battery containing a silicon negative electrode according to any one of claims 1 to 11 is adopted.